Both of them has their pros and cons, an onsite training seems more formal to me and there is a possibility to meet like-minded people. On the other hand online courses are accessible from around the world, no traveling is included to a distant location, so I might prefer this one (if the price is reasonable).
In the past there were lots of so called influencers, who tried to sell their low quality trading courses for a lot of money. One example is the infamous Bitconnect promoter Ryan Hildreth, whose crypto trading knowledge is questionable, but with good marketing he managed to sell his course to a lot of people.